Integrated cable guardrail system

ABSTRACT

A cable integrated guardrail system for highway guardrail. The rail of the system contains at least one cut section placed longitudinally along the panel, and of sufficient dimension as to allow interaction with a cable. Said cut sections also act to reduce longitudinal resistance and safely stop axially impacting vehicles. A cable, which is of sufficient length to extend longitudinally along the entire system, prevents tearing of the rail during lateral impacts and aids in safely redirecting the vehicle away from a hazard.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] U.S. Pat. No. 6,244,571

[0002] U.S. Pat. No. 6,220,575

[0003] U.S. Pat. No. 6,109,597

[0004] U.S. Pat. No. 6,022,003

[0005] U.S. Pat. No. 5,957,435

[0006] U.S. Pat. No. 5,775,675

[0007] U.S. Pat. No. 5,765,811

[0008] U.S. Pat. No. 5,407,298

[0009] U.S. Pat. No. 5,391,016

[0010] U.S. Pat. No. 5,078,366

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0011] NOT APPLICABLE

REFERENCE TO A MICROFICHE APPENDIX

[0012] NOT APPLICABLE

BACKGROUND OF THE INVENTION

[0013] The present invention relates to the general field of highway guardrail systems and roadside safety barriers. Principally, the invention is of an improved highway guardrail end treatment for guardrail barrier systems.

[0014] Highway safety devices utilized along most roadways consist primarily of guardrail barrier systems. W-beam guardrails are used to prevent vehicles from leaving the roadway and possibly colliding with fixed objects, other vehicles, or other safety hazards. For this, the semi-rigid guardrail barrier must be able to resist lateral impact forces, for instance a vehicle approaching at an angle to the length of rail. In this the barrier should perform in such a way that the vehicle is safely redirected back onto the roadway as opposed to tearing or passing through the guardrail.

[0015] The ability of guardrail to resist this lateral loading force is dependent upon a universally accepted corrugated shape, which dissipates the energy of the vehicle in a safe and controlled manner. However, the rigidity of w-beam guardrail is such that upstream, or terminal ends of a length of guardrail, can in itself present a hazard. Vehicles impacting the end section of a guardrail barrier without an appropriate terminal device encounter extreme forces that can lead to serious injury or death of the occupants. This problem of addressing terminal safety is a major area of research within the highway safety industry.

[0016] Recent design alternatives have placed emphasis on two main categories of terminal devices. Those terminals which gate the vehicle into a clear zone located behind the guardrail length opposite the roadway, and those that absorb the energy of the impacting vehicle through controlled dynamic buckling of the guardrail. Additionally, terminals can be either flared or tangent to the roadway.

[0017] Of the current terminal designs available, two are found to be the most widely used. Both systems are designed within the constraints of the currently accepted uniform standards, such that vehicles impacting at an angle to the length of guardrail are redirected away from the hazard. Functions during end-on impacts are design dependent to each terminal.

[0018] The first terminal system, is an energy absorbing safety treatment which utilizes a customized head assembly. This head unit functions to induce controlled buckling of the terminal guardrail, such that the vehicle is brought to a controlled stop after all impacting energy has been dissipated. The concept of this terminal has been applied to both flared and tangent applications.

[0019] The second terminal device, existing only as a flared gating system, utilizes slotted regions in the w-beam guardrail to reduce column strength in longitudinal impacts. A designed plate is set to maintain structural integrity during impacts, such that said slots do not tear and allow the vehicle to pass through the barrier.

[0020] Therefore, the intent of highway safety is to develop guardrail terminal systems which will address the issue of end-on impacts, and at the same time maintain adequate structural integrity to safely redirect vehicles during lateral impacts. Alternative designs to existing systems should provide equivalent or better safety performance values, as well as increase the availability of safety hardware through lowered costs, easier installation, and wide availability of common parts.

BRIEF SUMMARY OF THE INVENTION

[0021] The aim of the present invention is such that problems with guardrail terminal sections can be addressed at the lowest possible cost to the consumer. This is attained through utilization of common parts and the reduction in hardware items required. It is also the intent that the system comply with existing design standards and is easily interchangeable, in installation and components, to other competitive systems.

[0022] The present invention features a cable assisted rail terminal for use in conduction with standard highway guardrail barrier. The terminal is composed of w-beam rail cut to allow interaction of a cable within the plane of the barrier. These cut regions are of sufficient size and quantity to properly reduce the ability of the rail to resist buckling in response to longitudinal impacts. The invention utilizes the strength of the cable to appropriately dissipate lateral impact forces, such that the guardrail does not tear at those regions weakened, thus preventing the vehicle from leaving the roadway.

[0023] The cable, of sufficient length as to span the entirety of the terminal system, shares the load of impacting forces. The cable attachments shall be located such that during lateral impacts the force of the vehicle is dissipated into a ground anchor assembly, as opposed to directly through the guardrail beam.

[0024] This attachment of said cable is constructed of a common anchor bracket, known in the art, and to an anchor bracket of increased dimension from the standard item. The enlarged cable anchor allows direct connection of said cable to said ground anchor assembly.

[0025] It is intended that the present invention utilize a number of support posts to maintain structural height of the guardrail panels and cable. At least one of said posts is to be frangible, while the quantity and dimension of each shall be adjusted to meet industry accepted design standards.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0026]FIG. 1 is a plan view of the cable integrated guardrail terminal system in accordance with the present invention.

[0027]FIG. 2 is a side view of the system of the terminal of FIG. 1.

[0028]FIG. 3 is an exploded plan view of the double cable bracket attachment at the downstream portion of the terminal of FIG. 1.

[0029]FIG. 4 is a perspective view of the double cable bracket coupled to the system cable at the downstream portion of the terminal of FIG. 1.

[0030]FIG. 5 is a perspective view of the cable attachment to the system at the upstream portion of the terminal of FIG. 1.

[0031]FIG. 6 is a side view of the w-beam rail used in the terminal of FIG. 1.

[0032]FIG. 7 is a multi-angle view of the double cable bracket.

[0033]FIG. 8 is a detail of the cable as used in the terminal of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0034] The cable integrated guardrail terminal system of the present invention utilizes a cable running the length of the system to engage an impacting vehicle in tandem with the w-beam components of said terminal. The w-beam contains holes placed longitudinally along the face of the rail to weaken column strength in axial impacts. A cable of sufficient length is used to aid in the safe redirection of laterally impacting vehicles by preventing tearing of the rail at said weakened locations. The terminal system also aids in safely bringing vehicles to a controlled stop away from the protected hazard.

[0035] The preferred embodiment of the present terminal system is as an end-treatment for highway guardrail barriers. The terminal can be used in conduction with various other guardrail terminal anchorage systems, such as a breakaway cable anchor known in the art. The utilization of the system is to safely redirect laterally impacting vehicles back onto the roadway, and prevent vehicle spearing during end-on impacts. The system is intended to gate vehicles into a clear zone behind the guardrail barrier or bring vehicles to a controlled stop during axial impacts. The use of the terminal system is intended for all roadside applications, regardless of speed, made possible by modifying the w-beam components to fit expected impact conditions.

[0036] As detailed in FIGS. 1, 2, and 3, the terminal system consists of longitudinally corrugated guardrail sections (1) mounted to a number of support posts (2 & 3). System is intended to be attached to the downstream portion of a normal run of guardrail barrier at the most upstream post of the system.

[0037] As shown in FIG. 1, the system cable (7) runs the length of the system, attaching to an anchor bracket (8) at the upstream portion and to a double anchor bracket (6) at the downstream portion. This double anchor bracket (6) also connects a standard anchor cable (5) to the system. FIG. 1 also shows the intended post offset from the roadway, as utilized in the present invention, however, which can be modified to match installation criteria.

[0038]FIG. 2 details the cable on the traffic face of the guardrail, nested within the valley of the corrugated w-beam. The cable overlaps a hole proximate to the center of the valley, which is used to pass the cable from the front to backside of the rail.

[0039]FIG. 3 illustrates where the system cable (7) passes through the vertical plane of the w-beam (1) to the backside of the rail. The cable then attaches, via standard hardware, to the double cable bracket (6). A standard anchor cable (5), as used in the majority of present systems, connects the double anchor bracket to the base of support post 1 (3). A square plate washer (9) secures the cable (5) at the base of post 1 (3). As detailed in FIG. 2, this attachment distributes forces from laterally impacting vehicles into an anchor assembly, consisting of soil tubes (10) and a ground line strut (11). FIG. 4 shows an isometric view of the connection of the system cable (7) and the anchor cable (5) to the double cable bracket (6).

[0040] As shown in FIG. 5, the system cable (7), returns to the backside of the w beam after traversing the length of the system, to attach to a standard single cable bracket (8) prior to the most upstream system post (2). The cable attaches to the bracket via standard hardware.

[0041]FIG. 6 is a side view of the w-beam component in the present system design. Each of the three panels used in the current system are of the same dimension and hole placement.

[0042] The overall length of the w-beam section is 13′6″, with three post connection holes at 6′3″spacing and splice connections centered at 12′6″. The double cable anchor bracket in FIG. 4, (6), connects to the rail component immediately upstream from the most downstream cut section of panel one. The single cable anchor bracket, (8) in FIG. 5, attaches to the rail at the most upstream anchor box connection location. The system cable as shown in FIG. 1, (7), passes through the plane of the w-beam panel through the hole located proximate the centerline of the valley. This hole, in the current design, measures 2″ high by 4″ wide, and is centered proximate the middlepoint between each post hole location. The present invention utilizes two holes located proximate each peak in the w-beam component, shown in FIG. 6. These larger holes, presently measuring 1″ high by 16″ wide, are placed at the same longitudinal center as the pass-through hole mentioned above, midway between the post hole locations. The holes act to reduce column strength in the w-beam panel. This weakened section affects the cross sectional resistance to buckling in each panel, between each support post location, thus eliminating the potential risk of vehicular spearing during axial impacts. The location, quantity, and dimension of each hole can be altered based upon desired performance characteristics.

[0043] The double cable bracket, detailed in multiple angles in FIG. 7, is used in the present invention to attach the system cable to the w-beam component and the standard anchor cable. As shown in FIG. 7, the double cable bracket consists of a standard anchor bracket, known in the art and used separately in the present system, and an additional channel section welded to the exterior. A square washer is attached to the channel opposite the existing washer to provide a location whereto attach the system cable. The standard anchor cable rests inside the standard anchor box portion, and attaches to the square plate with standard nut and washer hardware. The system cable rests inside the external bracket chamber, and also attaches to the square plate via standard hardware. These connections can be seen in FIG. 3. This double anchor bracket, is connected to the w-beam component with standard hardware bolts and nuts, and can be modified in dimension and quantity to allow connections with additional cables, depending upon the requirements of the system.

[0044] The system cable, which acts to engage the vehicle during lateral impacts and prevent tearing of the w-beam components at the weakened sections by distributing the load, is shown in FIG. 8 as used in the present invention. The length of the cable is such that it extends longitudinally along the length of the system. The cable connects at one end to the double cable bracket immediately downstream of post 2, and at the opposite end to a standard anchor bracket located immediately downstream of post 7. The cable in FIG. 8, as used in the present system, consists of two swadged fittings attached to a ¾″ cable of the length shown in the detail. This length can be modified to extend over the distance required in any modification of the present system. 

1. A highway guardrail system for use along a roadside and having an upstream and downstream section, comprised of: a) a longitudinally corrugated rail having two peaks and one valley; b) at least one cut section along the rail, containing a hole of sufficient dimension to allow passage of a cable; c) at least one cut section along the rail, containing a hole of sufficient dimension to reduce the column strength of the rail during axial impacts; and d) a cable of sufficient length as to span the distance of the terminal system; and e) an anchoring bracket that connects said cable to an anchor assembly.
 2. The guardrail system of claim 1, wherein the cable is comprised of two swadged bolt fittings and standard anchor cable of said length.
 3. The guardrail system of claim 2, wherein the cable is attached at two positions, one being at the upstream end and the other at the downstream end of the system.
 4. The guardrail system of claim 1, wherein the rail is substantially parallel to the roadway.
 5. The guardrail system of claim 1, wherein the rail is flared at the upstream section away from the roadside.
 6. The guardrail system of claim 5, wherein the flare is parabolic.
 7. The guardrail system of claim 5, wherein the flare is straight.
 8. The guardrail system of claim 1, wherein the cut section is comprised of holes of necessary dimension located proximate the valley and each peak of the rail.
 9. The guardrail system of claim 8, wherein the cut section of holes are placed longitudinally along the length of the rail.
 10. The guardrail system of claim 1, wherein the upstream portion attaches to an adjoining guardrail barrier.
 11. The guardrail system of claim 1, wherein the rail is supported by one or more support posts.
 12. The guardrail system of claim 13, wherein at least one of the support posts is a frangible post.
 13. The guardrail system of claim 1, wherein the connection device for said cable to the system are comprised of cable anchor brackets.
 14. The guardrail system of claim 13, wherein at least one cable anchor bracket for the terminal system is of increased dimension to allow multiple cable attachment.
 15. The guardrail system of claim 13, wherein said enlarged cable bracket connects said system cable to a ground anchor assembly cable, known in the art. 